I submitted the following paper as the dissertation for a Magister Scientiae in History at the University of Edinburgh, August 2008, wherefrom I graduated with distinction.

Voltaire, d'Holbach and the Design Argument

1. Introduction

The seventeenth century saw fundamental changes not only in the practice of natural philosophy, but also in the justification of religion. By the second half of the century, the long-dominant Aristotelian natural philosophy was on the retreat and with it the intellectual authority of the scholastic tradition. The rise of Cartesian mechanistic philosophy on the Continent and of Baconian experimentalism in England had shifted natural philosophy into new avenues of enquiry and method.1 As experimental and inductive methods became increasingly accepted among leading European natural philosophers with the progress of the century, so too did their theological implications. The growing prevalence of empiricism called on new, empirical methods in demonstrating the truths of religion. Many clergymen, especially in England, were practitioners of natural philosophy and thus exposed to these novel intellectual currents. Likewise, many practising natural philosophers outside of orders were devoutly religious men, much concerned with reinforcing the foundations of Christian religious belief through their work. This meant that empirical natural philosophy was increasingly put to use in demonstrating the existence of God. With the decline of Aristotelianism, the scholastic a priori arguments for the existence of God were to a large extent superseded by a burgeoning tradition of natural theology in which the existence and attributes of God were to be demonstrated through meticulous observation of the physical world.2

The crux of this new natural theology was the 'argument from design', also known as the 'teleological argument' or the 'physico-theological argument.' Although it took many diverging forms, it was essentially an argument to the effect that the order and design observed in the workings of the natural world justified a belief in God as the designer of the universe. The orderliness of nature, combined with the intricate complexity of things both dead and living, were taken as evidence of purposefulness in the world. Without a purposive intelligence, went the argument, the world could not possibly exhibit these properties. Thus, there had to be a higher intelligence responsible for its creation.

Arguing for the existence of a higher intelligence from the intricacy of nature was not a novelty in the late seventeenth century. Historically, such arguments can be found as far back as the fifth century BC, in the writings of the Greek philosopher Anaxagoras.3 Throughout medieval times, however, the most widely disseminated formulation was that of Thomas Aquinas in the Summa Theologiae, where his "Fifth Way" of demonstrating the existence of God through reason was the following argument:

We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly do they achieve their end. Now whatever lacks knowledge cannot move toward an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.4

Aquinas' argument from the premise of teleology in the natural world to an intelligent source of purpose had gained new prominence by the end of the seventeenth century.5 Unlike many of the scholastic demonstrations of the existence of God, such as St. Anselm's ontological proof, it was an argument based on explicitly empirical premises, and thus congruous with the Baconian emphasis on induction spearheaded by the natural philosophers of the Royal Society. It is not surprising that the birthplace of natural theology was Bacon's home country, England, which in due course came to be regarded as the "cradle of natural religion."6 In the last decade of the seventeenth century, Isaac Newton brought all his authority to bear in support of this new natural theology, arguing that the universe, governed as it was by strict mathematically explicable natural laws, must be the creation of an intelligent deity "well skill'd in mechanics and geometry."7 In the second edition of the Philosophiae Naturalis Principia Mathematica (1713), he maintained that the arrangement and motion of the heavenly bodies "could only proceed from the counsel and dominion of an intelligent and powerful Being" and seems to have been much pleased that his natural philosophy could be put to use in demonstrating the truths of religion.8

The enormous influence of Newton on French eighteenth-century thought has been firmly established. Newton's methodological principles and natural philosophy, combined with the empiricist epistemology of his philosophical 'underlabourer' John Locke, formed the basis for much of French Enlightenment philosophy.9 The great influence commanded by Newton extended even to matters of religion. By the early eighteenth-century, France had developed its own tradition of natural theology with the works of the theologians Noël-Antoine Pluche and François Fénelon.10 As in England, the new supposedly empirical arguments for the existence of God carried authority outside church circles. Proponents of natural theology maintained that it was based on self-evident and compelling facts about the world, open to the examination of all, and could thus serve as a rational, scientific basis for religious belief. By the middle of the eighteenth century, acceptance of the argument from design had become so widespread, and so frequently was it invoked, that any discussion concerning the existence or non-existence of God was compelled to confront it. We see many examples of this in the philosophical writings of the times. Even violently anti-clerical philosophes such as Voltaire retained a belief in a creator-deity despite their antipathy toward revealed and institutional religion. The deism of Edward Gibbon, who was otherwise unafraid to submit even the most sacrosanct episodes of Christian history to the scrutiny of reason, speaks of the argument's power and influence.11 Another case in point is the philosopher La Mettrie, whose provocative materialist views scandalised fellow philosophes, but who still claimed to think "the greatest degree of probability ... in favor of ... the existence of a supreme being," given the intricacy of the natural world.12 Even the notoriously skeptical David Hume, for all his brilliant refutations of the design argument in the posthumously published Dialogues concerning Natural Religion (1779), saw fit to observe that "the whole frame of nature bespeaks an intelligent author."13 The centrality of the design argument to contemporary intellectual justification of religion meant that any would-be atheistic philosophy was compelled to address the apparent orderliness and design of the world and provide alternative explanations to those of natural theology. This makes the argument from design an important aspect of the eighteenth-century debate concerning the relationship between reason, religion and the foundations of religious belief.

In this dissertation, I use the works of Voltaire (1694-1778) and Baron d'Holbach (1723-1789) as a case study to highlight the tension in French Enlightenment thought surrounding the existence of God. The choice of these two philosophes is not arbitrary. The two have much in common. Both were prominent and widely read Enlightenment thinkers, much concerned with the effects of religion on the social and intellectual life of their times. Both, too, aggressively criticised revealed religion, and wrote extensively on what they perceived to be the pernicious influence exerted by institutional Christianity on the moral and intellectual progress of civilization; Voltaire in witty and ironic polemics, d'Holbach in serious, repetitive atheist tracts. Their influences were likewise similar -- both were much inspired by Locke and Newton, and by the works of the English deist philosophers Toland, Collins and Woolston, who had sought to rationalise the Christian religion by stripping it of its 'superstitious' elements.

For all their similarities, however, these two philosophes differed on a key issue: namely, the existence of God. To Voltaire, it was clear that the universe was the product of a divine craftsman -- a deity whose handiwork was everywhere evident in nature -- whereas for d'Holbach, in whose works French "materialistic and atheistic tendencies attained their fullest expression," the very postulation of a creator-entity outside of space and time was at best unhelpful in explaining the properties of the natural world, and at worst epistemologically impermissible.14

I argue that the disagreement between these two philosophes concerning the existence of a deity rested on their respective acceptance and rejection of the argument from design, which was in turn based on conflicting metaphysical and epistemological views. I examine these views and their foundations in the context of intellectual developments in eighteenth-century France, and argue that they reflect the increasing radicalism in French thought in the early second half of the eighteenth century. Drawing on a close analysis of primary sources, I begin with a study of Voltaire's numerous invocations of the design argument, and proceed to contrast his deism with the uncompromising atheistic materialism of Baron d'Holbach in the System of Nature (1770). Finally, I discuss Voltare's reaction to d'Holbach's writings, focusing on his refutations of the System of Nature in Questions sur l'Encyclopédie (1771), where he attacks d'Holbach's atheism and denounces the idea that the elaborate complexities of the natural world could be the product of anything except an intelligent creator.

2. Voltaire's God

Voltaire was one of the most persistent and widely read critics of established religion in the eighteenth century, and arguably the most polemical and effective publicist of the philosophes, ceaselessly mocking religious intolerance and superstition. His enormous corpus of writings amply demonstrates a thoroughgoing opposition to revealed and institutional religion in all its forms. Voltaire's exclamation écrasez l'infâme, urging for reform, became a rallying cry of the enlightened French intelligentsia, directed not only against the abuses of despotic government but also against institutional religions and their peddlers of "superstition and fanaticism."15 While his published works were cautious in their criticism of religion due to French state censorship, relying for the most part on analogies and ridicule rather than direct polemic, Voltaire's private letters reveal a deep-rooted antipathy toward revealed religion. Writing to Frederick the Great in 1767, he refers to Christianity as "assuredly the most ridiculous, the most absurd and the most bloody religion which has ever infected this world" and encourages the Prussian king to "do the human race an eternal service by extirpating this infamous superstition."16 Through seventeen hundred years, he writes, "Christianity has done nothing but harm."17 He regarded other revealed religions with no more favour, mocking Islam in Le Fanatisme, ou Mahomet (1741) as the invention of an insurrectionist "camel-merchant" who delivered his country "to iron and flame" in pursuit of a fanatical superstition.18

Despite Voltaire's persistent criticism and parody of revealed religion, few if any French eighteenth-century writers championed the cause of natural religion with as much ardour. Although he denounced Christianity, Voltaire was a deist and believed throughout his life in a single all-powerful and all-virtuous God.19 He thought it absurd to deny the existence of a creator-deity and tirelessly advocated a 'rational' form of religion, stripped of what he regarded as superstitious elements. What separated the religion of the masses from that of the rational man, he claimed, was the perversion of the former through authority and superstition. Christianity, Judaism and Mahometanism were corrupt and illegitimate extrapolations on a truth evident to all: namely, that there existed an intelligent and powerful designer-God, a Supreme Being who had created the world and the natural laws by which it was governed. Revelation was to true religion "what astrology is to astronomy, the foolish daughter of a wise mother."20 It consisted in embellished and mythologised variations on a fundamental, rationally ascertainable truth, put to use by unscrupulous people in exploiting the masses for their own ends. These superstitions were based on religious faith, which Voltaire regarded as irrational and vulgar. Faith was belief without evidence, and thus unacceptable. For his own deism, shorn of the institutionalised authority and historical baggage of Christianity, he claimed the backing of reason and common sense:

What is faith? Is it to believe that which is evident? No. It is perfectly evident to my mind that there exists a necessary, eternal, supreme, and intelligent being. This is no matter of faith, but of reason.21

Belief in God, Voltaire argued, did not require faith, since reasoning from observation could be used to infer the existence of a Supreme Being. A rational man who relied on the evidence of his senses could not help but acknowledge the handiwork of a great and intelligent creator in the features of the natural world. He would reject the falsehoods of priests and fanatics in favour of a deism firmly grounded in the proofs of natural religion.

Voltaire's deism developed relatively early in his life. In so far as deism constitutes belief in the existence of a Supreme Being and rejection of the supernatural doctrines of Christianity, he may be said to have been a deist from at least 1722, when he wrote his first philosophical poem, Le pour et le contre. In this poem, he eloquently expressed his antipathy towards Christianity and affirmed a vaguely rationalist, deist creed. The ensuing years only reinforced these views. In 1723, following a quarrel with a Parisian aristocrat, a lettre de cachet was issued for Voltaire's arrest, forcing him to flee to England. He stayed for two years on the other side of the Channel, mingling with prominent English intellectuals such as Lord Bolingbroke, Jonathan Swift, Alexander Pope and the Boyle lecturer Samuel Clarke, who introduced him to the English philosophical currents of the times. These years were in many ways crucial in forming Voltaire's later views, providing him with the intellectual ammunition to defend his deism and go on the offensive against revealed religion.22 Upon his return to France, he wrote and published the Lettres philosophiques (1734), seeking to acquaint his countrymen with the philosophical and political novelties of England. The Letters are widely recognised as the work that spearheaded the anglomanie -- the French preoccupation with English philosophy and English fashions that would last throughout most of the eighteenth century.23 They certainly did much to introduce the French intelligentsia to Bacon, Newton and Locke, who had by this time become Voltaire's new intellectual heroes.24

According to Voltaire, it was Francis Bacon who had inaugurated the great advances made in natural philosophy during the seventeenth century, and with his writings provided "the scaffold by means of which the edifice of the new philosophy" had been reared.25 Likewise, the "admirable" Locke had "laid open to man the anatomy of his own soul" by determining the ways through which men come to acquire ideas.26 However, it was the natural philosophy of Isaac Newton that proved to be particularly deep and lasting in its influence. Voltaire had been educated in the Aristotelian tradition of the Jesuits, but during his exile in England he was introduced to those "sublimest of discoveries" contained in the Principia Mathematica, wherein Newton had coupled the mathematical exposition of his physical laws with a mechanical, clock-like view of the universe.27 Voltaire adopted this new natural philosophy with enthusiasm, and from the 1730s and onwards he was a confirmed Newtonian, writing to Maupertuis -- one of the earliest proponents of Newtonianism in France -- that he was "a Newtonian of your kind; ... The more I glimpse of this philosophy, the more I admire it. One finds at each step that the whole universe is arranged by mathematical laws that are eternal and necessary."28

Newtonianism in England was at this time associated not only with the physical laws laid down by Newton, but also with a larger metaphysical system through which to interpret the natural world. Following the publication of the Principia Mathematica, many English natural philosophers and clergymen had quickly seized on the fact that the new natural philosophy might be used to stem what they believed to be a rising tide of irreligion, which they saw as rooted in materialist philosophies both homegrown and from the Continent, originating in the writings of Hobbes, Descartes and Spinoza. Of these scholarly defenders of the faith, the Boyle lecturers were probably the most influential. The natural philosopher Robert Boyle had left an annual sum in his will for lectures demonstrating the truth of the Christian religion "against notorious infidels," and in the last decade of the seventeenth century, Newtonian natural philosophy was enthusiastically adopted for this purpose.29

There was much in Newton's work that was open to different interpretations. The Boyle lecturers -- notably Samuel Clarke, Richard Bentley and William Whiston -- set about proving the existence of God by firmly resolving any ambiguities in Newton's philosophy in favour of a Christian God actively participating in the workings of nature.30 Samuel Clarke, a close friend of Newton and an acquaintance of Voltaire's, directly ascribed the operation of gravity to divine activity. At every moment, the mechanism of attraction between bodies depended on a Supreme Being actively imbuing matter with attractive force. Another Boyle lecturer, Richard Bentley, heartily endorsed Newton's belief in the existence of a divine maker who was particularly "well skill'd in mechanics and geometry," deducing this from the mathematical elegance of the inverse-square law of attractive force between bodies.31 Bentley also argued against Epicurean materialism, claiming that the paucity of matter in the universe made it well nigh impossible that it should have aggregated in such a way as to create the Earth and its creatures without divine intervention.32 In the "General Scholium" at the end of the third book in the second edition of the Principia, Newton himself had argued that the harmonious arrangement of the heavenly bodies could be explained only as the creation of an intelligent agent. It was quite inconceivable to him that the motions of the heavens could be the result of mere mechanical causes. The way to God was through his creation:

We know [God] only by his most wise and excellent contrivances of things, and final causes; we admire him for his perfections; but we reverence and adore him on account of his dominion.33

Newton thought that the natural world provided all the evidence necessary to demonstrate God's existence. A deity, in other words, could be inferred from the workings of nature, and such demonstrations were to be acknowledged as part of the practice of natural philosophy. With Newton's considerable intellectual authority behind them, English divines and natural philosophers thus gave birth to a tradition of natural theology that was intimately tied to the new natural philosophy, forming a comprehensive metaphysical worldview in which God played a crucial part.

It is largely through this tradition -- that is, within the context of Newtonian natural science and metaphysics -- that Voltaire defended and advocated his deistic beliefs. While he rejected the English Newtonians' Christianity, he wholeheartedly adopted three principal conceptions of their world view: the universality, constancy and uniformity of physical laws, the passivity of matter, and, crucially, the inference of a deity from the workings of the natural world.34 Drawing on Cicero's ancient argument, it seemed clear to him that just as a watch demanded a watchmaker, so the natural world required a mighty creator-craftsman.35 This argument for the existence of God appeared to follow the principles of Francis Bacon, whom Voltaire admired so much as the "father of experimental philosophy."36 In the Lettres philosophiques, he had enthusiastically advocated the inductive 'Baconian method' and lauded Bacon's attacks on the Aristotelian rationalism of the scholastics. The Baconian emphasis on inductive methods fit well with the arguments of natural theology. If the purely logical arguments for the existence of a God were, to quote Bacon's much-used metaphor, "cobwebs of learning, admirable for the fineness of thread and work, but of no substance or profit," the same was not the case with natural theology.37 Instead of relying on scholastic sophistry or Cartesian innate ideas, natural theology sought to demonstrate the existence of God through observation of the natural world -- sound empirical premises fully congruous with the Baconian method and with the principles of knowledge laid down by the 'admirable' Locke.

As they appear in his written works, Voltaire's arguments for the existence of a deity are a curious amalgam of appeals to natural theology, considerations of social utility, ad consequentiam reasoning and impassioned rhetoric. Aside from purely philosophical considerations, he was much concerned with the socially beneficial effects of belief in God. Although he sought to crush l'infâme of institutionalised Christianity, he believed, like Montesquieu, that religion was the most powerful force of moral constraint in society.38 Enlightened men might be 'natural friends of peace' and behave morally without the required fear of the afterlife, but the same would not be the case with the teeming masses. Without something to keep them in check, the common people would sink into depravity and iniquity. A society of atheists was unthinkable, a paradox, "because it seems impossible that men without constraint would ever live together ... a God of vengeance is necessary who will punish sinners who escape human justice, in this world as well as the next."39

A deity was also needed in order to address deeper metaphysical questions concerning matter, physical laws and the soul. From the Lettres philosophiques (1734) and his popular writings on Newtonianism through to the much later Dictionnaire philosophique (1764), a span of over three decades, Voltaire's essentially Newtonian metaphysical outlook stayed much the same. It was a system of which God was an indispensable part.40 The views that he had adopted from Samuel Clarke and the English Newtonians required not only a deity to create and form the material world, but one that imbued matter with the properties of motion and attraction. Since matter was by nature inert, yet still moved and exerted an attractive force, it had to have been somehow endowed with these properties. Likewise, the particular properties and behaviour of matter observed in the world -- the natural laws according to which the universe operated -- were, as Clarke had preached in his Demonstrations (1704), entirely arbitrary, and could have been altogether different.41 It had to be through divine will that they were so exactly constituted as to produce an ordered cosmos. And if the behaviour of matter demanded a divine source, the case was still more so with the soul. Thinking substance, too, presented a metaphysical problem. Voltaire's views on the soul are ambiguous and shifting, but he seems to have approved of Locke's speculations that God imbued matter with the property of thought.42 Both the phenomena of thought and the powers of attraction exhibited by matter were in need of explanation. For Voltaire, it was evident that explanation was to be sought in a creator-deity.

Metaphysical and moral considerations aside, it is the argument from design that recurs most persistently in Voltaire's philosophical writings on religious questions. Again and again, he stresses the complexity and orderliness of various phenomena in the world, and argues that they must be the creation of a great intelligence. Evidence of purposeful design, he maintains, is all around us in the spectacles of nature. Tracing the final causes of natural phenomena, we are compelled to conclude that they are the products of a purposeful maker. Epicurus and Lucretius, he writes, should be mocked for preposterously claiming that "the mouth is not made for speaking, for eating, the stomach for digesting, the heart for receiving the blood from the veins and for dispatching it through the arteries, the feet for walking, the ears for hearing." They were guilty of the outrage of denying to God what they accorded to the least of their workmen.43 The presence of complex, purposeful order in nature, on which the entire argument from design rested, and which Epicurus and Lucretius had the gall to deny, was in Voltaire's view self-evident to anyone who cared to look. The natural world provided compelling experiential evidence of a creator:

It is, it seems to me, to stop one's eyes and understanding to maintain that there is no design in nature; and if there is design, there is an intelligent cause, there exists a God.44

To lend his argument weight, Voltaire appealed again and again to common sense, emphasising in the Dictionnaire philosophique that "one must be blind not to be dazzled by this spectacle [of nature] ... one must be stupid not to recognize the author of it."45 Even the ignorant savage, untutored in the finer points of philosophy, intuitively recognised in nature the workings of a powerful, intelligent force. It was evident to him through the "natural logic which unfolds itself with age, even in the rudest of mankind."46 The complexity of natural phenomena and the fortuitous regularities of the natural laws governing the universe demonstrated a mighty maker. Purposeful order was as much evident in the smallest of creations as it was in the harmonious movements of the heavenly bodies. "The disposition of a fly's wing, a snail's organs suffices," Voltaire argued, to bring the "modern atheist" to the ground.47

The argument from design was not the only argument for the existence of God in Voltaire's philosophical arsenal. He freely mixed the cosmological argument -- that the world must have a cause, and that this cause was God -- with the argument from design, appealing in several of his writings to the maxim of nihil ex nihilo and the scholastic argument that a cause could be no lesser than its effect:

There is something; therefore there is something eternal; for nothing is produced from nothing. Here is a certain truth on which the mind reposes. Every work which shows us means and an end, announces a workman: then this universe, composed of springs, of means, each of which has its end, discovers a most mighty, a most intelligent workman. Here is a probability approaching the greatest certainty.48

Although Voltaire made use of both the cosmological and the design argument, he recognised the latter as the stronger of the two. As nature 'announces a workman' -- since we see teleology in nature -- we can draw inductive conclusions concerning the deity based on experience, whereas the cosmological argument relies on a priori principles of reasoning. In the Elémens de la philosophie de Neuton (1738), Voltaire notes with some satisfaction that Isaac Newton preferred it to the former.49 By invoking the authority of induction and empiricism, he saw himself as applying Newtonian and Lockean principles of reasoning in arguing for the existence of a creator. Locke had urged in his Essay Concerning Human Understanding (1690) that "Reason must be our last Judge and Guide in every Thing," and by relying on the argument from design to justify belief in God, Voltaire thought himself to be doing exactly that.50

For all this, it is important to note that Voltaire was in some respects more cautious in his treatment of the design argument than many of his contemporaries. When he dispenses with rhetorical flourishes and formulates the argument rigorously, e.g. in the Traité de metaphysique (1736), he speaks only of high probability and does not categorically rule out the possibility that there might be other explanations for the order observed in nature. 51 It is conceivable to him that the world might not be the product of a divine intelligence, although he thinks it overwhelmingly likely that this is the case. And for all his enthusiastic invocations of the argument, he was well aware of its logical limitations, as can be seen in the following passage from the Traité de metaphysique:

From [the argument from design], I cannot conclude anything more, except that it is probable that an intelligent and superior being has prepared and shaped matter with dexterity; but I cannot conclude from this argument alone that this being has made the matter out of nothing or that he is infinite in any sense. However deeply I search my mind for the connection between the following ideas -- it is probable that I am the work of a being more powerful than myself, therefore this being has existed from all eternity, therefore he has created everything, therefore he is infinite, and so on -- I cannot see the chain which leads directly to that conclusion. I can see only that there is something more powerful than myself, and nothing more.52

The order observed in nature indicated only the existence of a powerful, intelligent designer and could not provide any evidence concerning the properties of this creative force, which might or might not be the all-powerful creator-God conceived by Christians and deists alike. Belief in a definite conception of God went beyond what could be strictly inferred from empirical observation. Voltaire therefore urged that we must, like Cicero, "confess our ignorance of the nature of the Divinity."53 His understanding of the design argument was in this way more nuanced than that of many of the English Newtonians by whom he had been inspired. While they had taken natural phenomena as proof of the providence of the Christian God of revelation, Voltaire clearly recognised that this went beyond the argument's much narrower scope.

Although the design argument could not demonstrate the properties so often attributed to the designer, Voltaire thought it established beyond serious doubt the existence of a higher being of some sort. Consequently, atheism was not an intellectually respectable position. Pierre Bayle, whom he much admired, had written on the intellectually debilitating effects of superstition. Atheism was in Voltaire's view no better in this respect due to the metaphysical disorder it implied.54 If accepted, atheism made for a "universe of confusion."55 It rendered the world incomprehensible, inexplicable and purposeless, and deprived physical laws of the law-giver they seemed to require -- it destroyed, in other words, the providential cosmic order of Newtonianism as conceived by Samuel Clarke and the English Newtonians. Superstition and atheism were therefore two extreme, mistaken and dangerous poles; just as superstition was the "vice of fools," so atheism was "the vice of a few intelligent persons" who in their folly refused to acknowledge that which was evident.56 It is likely that Voltaire had d'Holbach and his circle of atheist friends in mind when he wrote this.

3. D'Holbach's Atheism

The philosophical and religious views of d'Holbach differed sharply from those of Voltaire. Paul Heinrich Dietrich, Baron d'Holbach was the most aggressively anti-religious of the French Enlightenment philosophers. Born in 1723, almost thirty years after Voltaire, he was a philosophe of the 'second generation,' counting among his friends men such as Diderot, Helvétius and Buffon. At an early age, d'Holbach inherited from his uncle both a noble title and a sizable fortune, which he put to use in pursuing and supporting various intellectual projects and charities. In time, his country seat at Grandval became, in the words of one contemporary, 'the café of Europe',57 visited by many of the greatest personages of Europe, including Wilkes, Walpole, Hume, Gibbon and Beccaria, to name but a few.58 His fame in his own times rested chiefly not on his written works, but his legendary generosity and his role as host to the most eminent philosophers and statesmen of the times.59 Nevertheless, d'Holbach was an impressive philosopher and natural scientist in his own right. He had an unusually thorough knowledge of natural philosophy, and has been described as "one of the most learned men of his day in natural science, especially chemistry and mineralogy."60 As a German who had become a naturalised Frenchman, he undertook the translation of many contemporary German works of natural philosophy into French, some of which wound up as articles in Diderot and d'Alembert's Encyclopédie.61 All in all, between 1751 and 1765 he contributed some four hundred articles to the project, mostly on scientific subjects, in addition to serving as the editor of several volumes on natural philosophy. 62 D'Holbach's knowledge of the sciences of his time was thus at a professional level, unlike that of Voltaire, whose abilities in natural philosophy never rose above the level of a gifted amateur.63

In the 1760s, d'Holbach gradually set aside his work in natural philosophy and became preoccupied with moral, political and religious questions. The three were to him intertwined, merely different aspects of philosophical issues concerning the wider task of bringing about social reform and moral progress. Under influence from the English and French deist writers of the early eighteenth century, he came to view religion not only as false, but as a morally pernicious social force, antithetical to human flourishing. In its stead, he hoped for the rule of a "true religion" consisting in

the art of advocating truth -- of renouncing error -- of contemplating reality -- of drawing wisdom from experience -- of cultivating man's nature to his own felicity, by teaching him to contribute to that of his associates; in short ... reason, education and legislation.64

D'Holbach's concerns were primarily moral. Like Voltaire, he saw the institutions of the Christian religion as a major obstacle to the improvement of society, and with his wealth and privileges, he set about writing and funding the publication of several anti-Christian atheist tracts over the following decades. D'Holbach's early writings were clearly modeled on those of critical English deists such as Toland, Annet and Collins, whose works had impressed him to such an extent that he translated several of them into French. For the most part, he focused on criticising the moral content and contradictions of Christian revelation rather than the intellectual foundations of religious belief as a whole, arguing that Christian teachings were in conflict with the dictates of reason and contrary to true morality. These propaganda texts, like Voltaire's, are rife with anticlericalism, rejection of miracles and original sin, and are invariably accompanied by a portrayal of the history of Christianity as one of fanaticism, ignorance and superstition. D'Holbach, however, exceeded both Voltaire and the most destructive of the English deists in the extent of his criticism of religion. As Diderot observed, he "rained bombs upon the house of the Lord."65

D'Holbach was careful to make his authorship of these anti-religious works a secret known only to his most intimate friends, often publishing them under the names of deceased English or French deists whose works he had perused. The first of his anti-religious tracts, the notorious Le Christianisme dévoilé (1761), he published under the name of the French deist Boulanger and the second, Contagion sacrée (1768), as John Trenchard, while his various other works and translations were attributed to a variety of authors, fictitious or deceased.66 Many were published secretly in Amsterdam and smuggled into France, thus bypassing the French state censorship. In this way, d'Holbach managed to write and publish a great deal of provocative anti-religious literature whose true authorship was unknown outside of a small, tightly-knit circle of philosophes. His caution is understandable, given the series of humiliating retractions his friend Helvétius had been obliged to make following the furor surrounding the publication of De l'esprit in 1758.67

D'Holbach's greatest work, the System of Nature, was published in secrecy in 1770 under the name of J. B. Mirabaud, a secretary of the French Academy of Science who had passed away ten years previously. It was an extremely radical anti-religious work, and went much further than any of d'Holbach's previous writings -- or, indeed, any other pre-Revolutionary work -- in attacking the principles and foundations of religion. While d'Holbach's early works had mostly focused on criticising Christian doctrines and Scripture, the System of Nature rejected religion tout court, be it natural or revealed, outlining in its stead a comprehensive, systematic and highly developed materialist philosophy which left no room whatsoever for divine agency in the making or function of the world. Upon publication, the System of Nature immediately raised a storm in France and soon enjoyed a notoriety unmatched by any of the works of d'Holbach's contemporaries.68 It is on the basis of this work that d'Holbach's philosophy has been called "the culmination of French materialism and atheism."69 Its radical empiricist and materialist principles run as a philosophical undercurrent through all of his subsequent writings, including Le Bon Sens (1772) and the later political and ethical writings, and represent his most developed thoughts on metaphysical and religious questions.

For all the controversy it stirred up, it is generally recognised that the System of Nature was not a particularly original work.70 There is some truth in this, as many of its principles and arguments were either directly taken from the works of the English deists d'Holbach admired, or to be found in earlier works by Diderot, who was undoubtedly a large influence. The debt of d'Holbach's materialism to that of Diderot has been a source of some contention, for although the two were close friends and unquestionably influenced each other's views to a large extent, it is in many cases far from clear who was influencing whom. Unlike Diderot, however, d'Holbach did not merely flirt with materialist ideas in his written works. The former was an unsystematic thinker, and his thoughts on religion and materialism are interspersed throughout many different works, often in the guise of fiction, as in the case of Le Rêve d'Alembert (1769). Protected by a cover of strict anonymity, d'Holbach was free to be much more forthright than Diderot in expounding his principles, and was the only philosophe to publish a fully worked-out materialist philosophy, applying it unreservedly to a wide range of questions concerning religion.71 His genius lay in synthesising the various anti-religious and materialistic philosophies of the preceding 150 or so years into a coherent and comprehensive whole. This makes him an excellent representative of eighteenth-century French atheism in its most radical and immaculate form. If Voltaire is in many ways the archetypical French Enlightenment deist, then d'Holbach, in his dogmatic, relentless and unsparing critique of religion, may certainly be viewed as the arch-atheist.

D'Holbach's major influences were mostly English. He borrowed generously from Hobbes, Locke and the critical deists, but like most of the philosophes, he was particularly influenced by the empiricist philosophy of Locke, which he adopted and subverted for his own ends.72 Like Voltaire, he rejected the notion of innate ideas and believed that all knowledge was necessarily grounded in primitive, irreducible sensory experience of nature. His empiricism, however, was much more extreme and anti-metaphysical.73 This is hardly surprising, for Voltaire had been at the forefront of the current that brought English empiricism and natural philosophy to France in the 1720s and 1730s, whereas d'Holbach was part of a later group of radicals to whom these English influences had become commonplace, often better known to them through the sensationalist psychology and epistemology of Locke's French counterpart, the abbé Condillac.74 Like Helvétius, d'Holbach took what he wanted from Locke and made it his own, discarding the English philosopher's metaphysical views. He gave a completely materialist turn to Locke's empiricism, dispensing completely with the concept of the soul, and like La Mettrie, he made all the crucial terms in his psychological vocabulary -- 'ideas', 'sensations' and 'perceptions' -- correspond strictly to changes in man's internal physical organisation, thus substituting Locke's metaphysical underpinnings for a thoroughgoing materialism.75

The inspiration for d'Holbach's materialism dated from the previous century. His library shows that he was intimately familiar with the metaphysical debates of the seventeenth century between Malebranchists, Cartesians and Aristotelians, which were characterised to a large extent by mutual polemical accusations of materialism and atheism by the parties involved.76 Likewise, he was heir to the seventeenth century's interest in Lucretius and Epicureanism, which did much to form his view of nature.77 Nature is a central concept in d'Holbach's philosophy, signifying the totality of the material world in all its manifestations -- "the great whole, that results from the collection of matter, under its various combinations ... which the universe presents to our view." She is a "vast circle of generation and destruction" without beginning or end, strictly determined by inexorable, strictly necessary physical laws.78 D'Holbach's conception of nature thus differed significantly from Voltaire's divinely crafted and providentially ordered world.

While Voltaire and d'Holbach differed both concerning the nature of matter and in their interpretation of Lockean empiricism, the two agreed that demonstration of the existence of God ultimately had to rest on observation, and that knowledge of a higher being must be acquired "through the medium of nature."79 Unlike Voltaire, however, d'Holbach did not think that the spectacle of nature justified belief in a higher intelligence, and was not at all persuaded by the argument from design, which to him did nothing to answer the question of why the world was orderly and contained complex phenomena. Not only was the notion of 'order' on which the argument rested a highly problematic and misconceived one -- the very postulation of a designer-God to explain it only raised further questions. There was in his view "no necessity to have recourse to supernatural powers to account for the formation of things."80 Recognising the prevalence of natural theology and natural religion -- the purportedly 'rational' bulwark of religious belief -- amongst his English and French contemporaries, he devoted several parts of the System of Nature to directly or indirectly discrediting the design argument and the premises on which it rested.

In contrast to Philo in Hume's Dialogues, d'Holbach did not focus his attack on the argument from design by pointing out the weaknesses of reasoning by analogy, founding it instead on a rigorous empiricist epistemology and a psychological analysis of man. His refutation of the argument from design is twofold. Firstly, he denies that order or purposefulness is a property of objects in the universe, ascertainable empirically in the same way as other properties. Secondly, he argues that the postulation of an intelligent designer is epistemologically impermissible from an empirical standpoint, regardless of whether order and purpose can or cannot be discerned in the workings of the natural world.

The first of these, d'Holbach's denial that order is a feature of the world, is crucial to his refutation of the design argument, and hinges on his essentially Epicurean materialist view that the universe is bereft of any intrinsic teleology. Our notion of order, he says, is an empirical one, much like any other, and deserves no special treatment. If we ask what sensory perceptions give rise to the concept of order, we find that our experience is only in respect to the ends of human beings, i.e. we are solely familiar with it in our own minds. The conception of order is thus a reflection of our ends. As thinking beings we are continually in the process of creating our own ends, and we come to interpret the natural world in terms of them. This does not, however, mean that these ends are in any way an inherent part of nature, existing prior to our perception of them. Order and confusion are ultimately the product of our imagination, which provides us with a model for evaluating what is orderly and what is not. As conscious, thinking creatures, we find certain arrangements and states of affairs conducive to our ends, and others inconducive, and these come to be deemed orderly or confused according to their congruity with our purposes. In the grand scheme of things, the great earthquake of Lisbon is no more a disorder in nature than the tranquility of the gardens at Versailles. Freaks of nature, animals deformed at birth or in life, meteorites, roaring thunderstorms and lightning -- through the ages interpreted as wrathful interventions of one or more deities in an otherwise divinely ordered world -- none of these are examples of actual confusion or disorder, for the alleged confusion is "always a necessary consequence of the laws of Nature."81 Before her every state of affairs is equally ordered or disordered, merely a combination of successive arrangements of matter in perpetual motion, in which any given state is the necessary result of a previous state. Only through the anthropocentric spectacles with which we view the world can terms like 'order' and 'disorder' properly be used. They are the product of man's unavoidably teleological perception of the world and "can have no absolute existence in Nature."82

Given this non-teleological view of nature, d'Holbach argues that inferring purpose from any of its functions goes outside the boundaries of strict empirical reasoning and is therefore rationally unjustified. Teleology is a feature not of the world, but of man's pyschology. The supposedly orderly features of the natural world do not, as the natural theologians proclaim, present clear cases of purpose from which one can infer the existence of a designer. On the contrary, if we are objective and manage to transcend our habitual mode of perceiving things, we will see that order in the world represents

nothing more than a mode of considering, a facility of perceiving ... the different relations of a whole; in which is discovered, by its manner of existing and acting, a certain affinity or conformity with [our] own.83

D'Holbach thus explains -- or rather, explains away -- order in nature as a matter of epistemology. The "order, which we admire as a supernatural effect" is not an effect at all, but in fact the cause of all effects.84 Nature is a self-contained, self-causing, eternal series of matter in motion, which is mistakenly conceived as being directed to some end or ends above and beyond those of man.85 Ultimately, the perceived order within it has "no existence but in [man] himself."86

Although order per se might be in the eye of the beholder, depending on congruity with human purposes, d'Holbach concedes that the world exhibits underlying regularities in the form of natural laws governing the motion of matter. These regularities, he maintains, do not provide any grounds either for assuming the work of a higher being, for there cannot be any role for chance in nature. Voltaire and the English Newtonians were mistaken in believing that the laws of nature are arbitrary, subject to the purposeful will of a benevolent creator. Nature has in fact a "mode of existence ... strictly necessary."87 The underlying regularities that she exhibits must be the way they are, and not otherwise, for we cannot even conceive of an irregular, disordered universe except in terms of our own subjective ends and purposes. With time, even the most heterogeneous substances, thrown together in extraordinary and seemingly disordered circumstances, come to an orderly form, given the operation of any law-bound behaviour. "In every assemblage of causes and effects," d'Holbach concludes, "some kind of order would necessarily be established."88 Regularity of natural laws therefore cannot serve as evidence of divine providence.

In a style reminiscent of Hume, d'Holbach supplements his arguments against extra-human teleology in the world with a naturalistic explanation of why such views come to be so widely acknowledged and accepted. Drawing on Spinoza, he maintains that human beings have a natural psychological propensity to anthropomorphise nature.89 They cannot help but project their own goals and purposes on to a world of constantly shifting and changing matter whose motion is in fact governed by universal laws wholly indifferent to their ends. Nature proceeds by necessity from one state to the other without intent, design or purpose. Men, like any other matter, are part of the whole process of nature, and are "moved or determined by some exterior cause."90 In a complex world of interlocking causes, they behold much that they do not comprehend, and in an attempt to understand the mysterious, they attribute to it their own goals, intentions and purposes. Grasping for an explanation of natural phenomena, they come to "believe there is a supernatural agency, in all those objects to which their eyes are unaccustomed."91 Natural events therefore come to be seen as the result of activity by some secret or hidden causes, "instruments, employed by some invisible agent ... either friendly or inimical to [their] welfare."92

Like Hobbes, d'Holbach thought that this propensity to interpret matter and motion in terms of the workings of a higher intelligence was an apparatus of psychological and intellectual relief. It was "the ignorance of causes," and the fear that this ignorance instilled, that gave birth to the gods.93 That which man does not comprehend frightens him, but once a thing has been explained, once its causes seem to have been unravelled, it ceases to be terrifying. Whether the explanation given is true or not is irrelevant to the psychological effect. As soon as the mysterious is rationalised, man's fears diminish and "his mind becomes calm, in proportion as experience familiarizes him ... with natural effects; his fears cease entirely, as soon as he understands, or believes he understands, the causes that act."94 This psychological mechanism is the reason why intelligent men, otherwise impervious to the superstitions of the masses, retain faith in a deity. The postulation of one or more intelligent deities governing nature renders the world superficially less mysterious, for we can apply our own human teleological categories -- of intent, purpose and design -- in describing and interpreting them. The hypothesis of the designer-God, d'Holbach concludes, is nothing more than a psychologically understandable but ultimately intellectually unjustified way of making the unknown more familiar -- and thus less intimidating.

In the fifth chapter in the second volume of the System of Nature, d'Holbach specifically addresses the analogy of the watch and watchmaker so often invoked by Voltaire and the proponents of natural theology. His rebuttals lack the subtlety and ingenuity of Hume's Dialogues, and rest entirely on his presupposition of materialism and his Hobbesian analysis of religious psychology. The entirety of nature, d'Holbach maintains, cannot fairly be compared with a watch created by a watchmaker, since nature by definition encompasses everything. We may view the spectacles of the natural world with awe, much as a savage admires the constructions of civilised men, but nothing should persuade us that they are in any sense above nature, for "nature is competent to every thing: as soon therefore as a thing exists, it is proof she has been capable of producing it."95 In other words, d'Holbach rejects the analogy by fiat. If something exists, it is the product of nature. It is only due to "our own peculiar ignorance, and the weakness incident to our nature" that we come to believe otherwise.96 Only when man cannot fathom the causes of things does he insist they "are impossible to be the productions of nature, although he is entirely ignorant how far the powers of this nature extend."97 Instead, he adopts the more psychologically gratifying explanation of the purposeful creator-God.

D'Holbach's second major attack on the argument from design is his categorical rejection of the concept of the creator-God as a coherent or intelligible explanation of nature and its properties. Basing his objections on a combination of appeal to empirical principles and sheer rhetoric, he attempts to demonstrate the explanatory poverty of postulating a designer-God as the creator and organiser of the world. By positing an intelligent creator, he asks, have we really explained anything? When man attributes the wonders of nature to the masterful craftsmanship of God, "does he, in fact, do any thing more than substitute for the darkness of his own mind, a sound to which he has been accustomed to listen with reverential awe?"98 To d'Holbach, the answer is clearly negative. "The word GOD," he maintains, "is for the most part used to denote the impenetrable cause of those effects which astonish mankind" but is in fact just as impenetrable as the effects it is to account for.99 This is necessarily so, because nature is the totality of everything. It is time and space, and all the matter within it. Our acquaintance with anything external to it is an impossibility, since all our genuine knowledge is ultimately derived from empirical foundations. We cannot legitimately permit ourselves conjecture and inference concerning extra-natural entities. We cannot even conceive of a divine workman outside of time and space, since we have not, and cannot have, experience of him. Borrowing from the theologian Noel Aubert de Versé, d'Holbach asks: "Where shall we place this workman? Shall it be exterior or interior to his production?"100 Both are an impossibility. God would either be nothing, or he would be contained in nature and therefore subject to her laws, rather than their author. Either case would make it impossible for him to have created the phenomena of nature. The theory that a higher intelligence created the world and organized the matter within it is thus not only misguided and incoherent -- it is a plain impossibility, and does nothing to address the difficult questions concerning creation and design. Take for example the question "Whence came man?", the creature seen by so many natural theologians as the paradigmatic example of divine craftsmanship. D'Holbach does not think that this question is one of any great importance and maintains that our experience "does not capacitate us to resolve [it]."101 While we may venture hypotheses in an attempt to answer it, these can never be more than tentative and cannot be the basis for religious truths. If we are to hypothesise at all, it should at least be coherent and throw some light on that which is to be explained, but this is not the case, he argues, with explanation in terms of a deity:

We are incessantly told to acknowledge and revere the hand of God, of an infinitely wise, intelligent and powerful maker, in so wonderful a work as the human machine. I readily confess, that the human machine appears to me surprising. But as man exists in nature, I am not authorized to say that his formation is above the power of nature. But I can much less conceive of this formation, when to explain it, I am told, that a pure spirit, who has neither eyes, feet, hands, head, lungs, mouth nor breath, made man by taking a little clay, and breathing upon it.102

In other words, the designer-God is in his view a pseudo-explanation, leaving us no better off in terms of real knowledge since it raises questions that are even more difficult to answer than those which it is meant to address.103

D'Holbach's own speculations concerning the origin of man are significant, for they show that, like Diderot, he was groping toward something akin to an evolutionary or developmental process to explain the diversity and complexity of living things.104 "Has man," he asks, "always been what he now is; or has he, before he arrived at the state in which we see him, been obliged to pass under an infinity of successive developements?"105 Proclaiming his intellectual kinship the English experimenter John Needham, who had detected 'spontaneous' generation of life in blighted wheat, d'Holbach deems it more probable that man is "a production formed in the course of time."106 He is careful, however, to emphasise that these are mere hypotheses, and not integral to his system. The questions concerning the origin of life, he concludes, are difficult to answer and may forever elude our understanding since we are not in a position to obtain the experience necessary to resolve them.107 Whatever the origins of man and other creatures, their existence as such does not lend any weight to the existence of a deity, for our lack of understanding does not allow us to hold purely conjectural and empirically ungrounded hypotheses in order to plug the gaps in our knowledge of causes.

D'Holbach clearly regarded his extensive battery of arguments as destructive of all religion, not just that of revealed Christianity. Any postulation of a higher intelligence was illegitimate due to the strictures of empirical reasoning. The supposed claims of common sense and empirical foundations made by the proponents of natural religion were only superficial trappings masking fundamentally irrational beliefs. Not only was natural theology based on faulty premises, it also failed to provide cogent answers, and therefore could not be used to demonstrate the existence of deity. This meant that natural religion was just as misguided as that based on revelation. In discussing the connection between natural religion and the deists of his time, d'Holbach thus remarked that while the deists might be "undeceived upon the greater number of grosser errors which the ... superstitiously ignorant ... support," they nevertheless went outside the boundaries of possible knowledge.108 The difference between the deist belief in a remote higher being and the basest forms of superstitions was merely one of degree, and therefore there were "no substantive grounds for separating the theists from the most superstitious."109 Both were victims of their imagination; once it was permitted to venture beyond the strictures of experience, it would be "impossible to mark the point at which imagination ought to arrest itself."110 To any man of sound reasoning, positing a higher intelligence as the explanation for the complexity of nature must therefore be highly unsatisfactory. He would do better to acknowledge his ignorance of causes and channel his energies towards problems more amenable to resolution.

4. Voltaire's Reaction

The Catholic theologian Nicolas Sylvestre Bergier, an early critic of the System of Nature, was quick to recognise that the atheistic materialism of d'Holbach and his circle presented a significant challenge to deist views such as those of Voltaire, and anticipated a wholesale capitulation of deism into atheism among the philosophes.111 He was certainly mistaken in regard to Voltaire, who remained adamantly hostile to d'Holbach's views throughout his life. Denying the authorship of Christianisme dévoilé in 1761, he made known his aversion to d'Holbach's philosophy, writing that "[the work] is entirely opposed to my principles. This book leads to an atheistic philosophy that I detest."112

By the summer of 1770, copies of the System of Nature had begun to circulate clandestinely and one of them found its way into Voltaire's hands. From his letters, it is clear that the work agitated him. Troubled by its arguments and fearful of the social consequences that overtly atheistic literature might bring about, he describes it as "a book that has made much noise among the ignorant, and that shocks all men of good sense."113 Irrespective of the danger Voltaire saw in promulgating atheism, d'Holbach's materialist philosophy constituted a direct challenge to his own metaphysical views. Thus, in the wake of the storm of controversy raised by the System of Nature, he specifically addressed its author in 1771 in an addendum to the Questions sur l'Encyclopédie, in the entry "Dieu - Dieux," parts of which were published separately in 1770. He was well aware of the identity of the author of the System of Nature, and thought that he was "to be distrusted both in physics and in morals."114 Voltaire was at this stage 76 years old, and his reply to d'Holbach indicates deep concern with the direction in which the philosophe movement was heading. The sort of enlightenment envisioned within the coterie holbachique -- materialistic rather than metaphysical, atheistic rather than merely anticlerical -- was one that was anathema to him, being in his view both dangerous and guilty of fundamental philosophical errors. It is telling that his response, "Du Système de la Nature," immediately followed a refutation and indictment of the philosophy of Spinoza, for d'Holbach and Spinoza posed similar threats in their rejection of final causes. Both envisioned a monistic world, bereft of intrinsic purpose or teleology, in which man was an unprivileged part of nature and subject to mechanistic explanation much like any other phenomenon.

In terms of arguments, Voltaire's reply to d'Holbach in Questions sur l'Encyclopédie brought nothing new to the table, making use of much the same arguments and rhetoric that he had employed in his many other works: common-sense appeal to the purposiveness evident in the frame of nature, combined with mockery of alternatives to theistic explanation of the world. It is significant that Voltaire was particularly outraged by d'Holbach's claim that order and disorder did not exist in nature. "What!" he exclaims, "Is not a child born blind, without legs, or a monster, contrary to the nature of the species?"115 By rejecting the divinity and ascribing everything to the operation of matter, d'Holbach had rendered the very concept of being 'natural' redundant. In his anti-teleological worldview, nature encompassed and was the cause of everything that existed, and thus nothing could properly be said to be 'natural' or 'unnatural,' irrespective of common sense intuitions. The conclusions of this were in Voltaire's view unpalatable. A malformed child was to him as clear and unambiguous a sign of disorder in nature as the assassination of one's brother was in morals. While we might very well be ignorant of the source of disorder in nature and morals alike, this did not justify d'Holbach's conclusion that they did not exist outside of human ends.

Nor did Voltaire think much of d'Holbach's refutations of the design argument, addressing none of them head on. The materialism through which d'Holbach would dispense with an intelligent creator was in his view underdetermined by evidence and rested entirely upon speculative premises. Furthermore, d'Holbach's lack of concern with addressing metaphysical questions incensed him. For all his disparagement of the 'system builders' of the previous century, and his ridiculing of Leibnizian and Wolffian metaphysics in Candide (1759), Voltaire was much concerned with metaphysical issues, and his many disavowals of "confusion" in the world show his desire to resolve metaphysical questions in such a way as to make the world orderly and meaningful.116 D'Holbach, on the other hand, was both more cautious and more dismissive in these matters. To Voltaire, this was a fatal flaw: D'Holbach could not prove that his materialism was true, and yet it was on this basis that he rejected the existence of God. It was shaky ground from which to mount an attack against the 'natural logic' of mankind. Addressing d'Holbach, he writes:

When you venture to affirm that there is no God, that matter acts of itself by an eternal necessity, it must be demonstrated like a proposition in Euclid, otherwise you rest your system only on a perhaps. What a foundation for that which is most interesting to the human race!117

Voltaire realised that he himself could not absolutely demonstrate the existence of God, and relied instead on probabilities that he thought to be strongly in his favour. But likewise, d'Holbach could not demonstrate the non-existence of God, or even his probable non-existence. Voltaire threw down the gauntlet, demanding that the author of the System of Nature show him plainly that his "intelligence [could not] have been given ... by an intelligent cause."118 Since d'Holbach could not demonstrate it, his atheism rested 'only on a perhaps' and therein Voltaire perceived his advantage. Atheistic materialism left many metaphysical questions unanswered which he believed the postulation of a creator-deity could firmly address.

Special ridicule was reserved for d'Holbach's speculations concerning the origins of life. Although these were peripheral to his materialist philosophy and were given relatively short treatment in the otherwise lengthy System of Nature, it is the notion that life could generate spontaneously through natural processes that bore the brunt of Voltaire's sarcasm in Questions sur l'Encyclopédie. The System of Nature, he claimed, was ultimately founded on a 'Story of the Eels.' Here Voltaire was referring to the work of John Needham, an English clergyman and member of the Royal Society who with his microscope had observed organisms, tiny eels amongst others, generating in grains of blighted wheat. As mentioned earlier, d'Holbach had referred to Needham's work as evidence that the generative powers of nature were much greater than commonly supposed, indicating that nature itself could be the cause of life. Spontaneous generation at the hands of nature went very much against Voltaire's belief in preformation at the hands of a deity. The animal kingdom, which furnished such abundant examples of divine craftsmanship, could not possibly, in his view, be the product of processes in wheat flour. To produce intelligence without intelligence was an idea that was patently absurd. In one of Voltaire's letters, written in 1770, the System of Nature is quite unfairly dismissed as being entirely founded on a "false experiment made by an Irish Jesuit who has been mistaken for a philosopher."119

All in all, Voltaire did everything he could to discredit the System of Nature, regarding d'Holbach's attempts to show that the world was self-caused and self-contained -- "that this house ... built itself" -- as based upon an "astonishing error."120

5. Conclusion

Voltaire's adamant opposition to d'Holbach's materialism and atheism, as we have seen, was rooted in irreconcilable philosophical differences. These differences may at least partly be explained by the generational gap between the two philosophes, and are best understood in the context of the developments in radical French thought from the middle of the eighteenth century and onwards. Voltaire had been at the very forefront of the movement that brought late seventeenth-century English Enlightement philosophy to France. His intellectual outlook was substantially shaped in the 1720s and early 1730s, and did not undergo any fundamental changes in the ensuing decades. The enlightened Newtonianism he preached with such vigour -- deism, a natural philosophy of attractive forces, and adulation of Bacon, Locke and Newton -- was at the height of intellectual fashion in Paris in the late 1730s and 1740s, when it was an exciting novelty with many supporters,121 but by the late 1740s, the 'English philosophy' had suffered setbacks, challenged by d'Alembert and many of the encyclopédistes, who called themselves Newtonians but had in fact subverted the original Newtonianism by stripping it of its dependence on divine contingency.122 Far removed from Paris in his country house at Ferney, Voltaire had by 1770 become out of touch with the radical fringe of French thought, which had largely moved away from his deistic, Newtonian-Lockean philosophy. The younger generation of philosophes publishing in the late 1740s through the 1760s -- particularly Helvétius, La Mettrie and d'Holbach -- tore English natural philosophy and empiricist epistemology from its metaphysical roots and developed it in new directions that were at odds with those of the English Newtonians who had given birth to it. This is particularly well reflected by the absence in their works of the hero worship of Newton so typical of Voltaire and the English Newtonians. Newton had been for them an authority not only in matters of natural science but in metaphysics also, whereas this was not the case with the radical encyclopédistes.123 For all their praise of his scientific discoveries, d'Holbach, d'Alembert and Diderot regarded Newton's providential, millenarian religious views as pathological, and thought his metaphysics suspect. This "father of modern philosophy," whose genius had unmasked the laws of motion, was to them a mere "infant when he quit physics ... a slave to the prejudices of his infancy."124 While they recognised his work in natural science as an achievement without parallel, he was no authority to them in matters of religion or metaphysics.

Voltaire's response to d'Holbach's System of Nature, as we have seen, was to ridicule it and defend his own conception of enlightenment with sword and shield. Having brought Newtonianism and Lockean empiricism to France, he stuck tenaciously to the metaphysics adopted in his younger years. However, the general intellectual climate in France had undergone substantial changes since the publication of the Lettres philosophiques. Voltaire's philosophy was no longer at the very forefront of controversy, having given way to that of the radical wing of the philosophes. Works like De l'esprit, L'homme machine and the System of Nature supplanted his writings as the most scandalous and subversive literature of the day. It was the new generation of radical materialist philosophes who now provoked outrage among reactionaries, just as Voltaire's own writings had done 30 years previously. Voltaire's reaction to these developments was mixed, and his correspondence with Diderot bears witness to mutual unease. Although the new radicals were allies in the battle for intellectual and social reform and sought, like Voltaire, to undermine the powers of the clergy in France, their philosophies -- particularly those of d'Holbach and La Mettrie -- were in his view so extreme in their anticlericalism and so atheistic as to bode ill for society as a whole, which required a providential order based on divine authority to regulate the behaviour of men. Thus, Voltaire's public interactions with the clerical authorities were relatively tactful. D'Holbach, however, attacked religion not only when it manifested itself in superstition, wilful ignorance and institutional abuse, but even "when it is useful to society."125 In opposing these materialist and anti-religious developments among the philosophes, Voltaire was thus in the position of defending 'orthodox' French Enlightenment philosophy -- English-inspired, providential, anticlerical and deistic -- against subversion by a generation of much more radical thinkers, among whom d'Holbach was perhaps the boldest.

In conclusion, the differing approaches of Voltaire and d'Holbach to the argument from design aptly demonstrate the differences in their metaphysical views, the most important of which was their conflicting views on natural teleology. We have seen that despite their shared war on revealed religion and concerns with social reform, they regarded the question of design in nature from diametrically opposed angles. Where the former saw divine, purposeful order announcing a great creator, the latter saw only law-governed, self-moving matter in no drastic need of further explanation. The fundamental philosophical differences between these two worldviews marks a decisive split between the 'moderate' and 'radical' wing of the philosophes and highlights the growing radicalism of French Enlightenment philosophy in the first two decades of the second half of the eighteenth-century.

12. Julien Offray de La Mettrie, Man a Machine (London, 1749). For a discussion of La Mettrie's thoughts on design in nature, see Jonathan Israel, Radical Enlightenment: Philosophy and the Making of Modernity, 1650-1750 (Oxford University Press, 2001), p. 704-712.

13. David Hume, Four dissertations. I. The natural history of religion. II. Of the passions. III. Of tragedy. IV. Of the standard of taste. By David Hume, esq. (London, 1757), p. 1.

15. The phrase 'écrasez l'infâme' ("crush the infamy") is used by Voltaire in many of his letters. See e.g. letter to Jean le Rond d'Alembert 1762-11-28 in Voltaire in his letters: being a selection from his correspondence / translated with a preface and foreword by S.G. Tallentyre (London, 1919).

35. The first occurrence of the watchmaker analogy is unclear. In De natura deorum, Cicero used the waterclock as an analogy for divine craftsmanship. Descartes also used the clock as a metaphor for mechanism in the Discourse on Method, while the actual use of the term 'watch' occurs in Robert Hooke's Micrographia (1664) concerning the mechanistic intricacy of insects. As a direct analogy for the design argument, it may first have appeared in William Derham's Artificial Clockmaker (1696).

54. For a discussion of Bayle's analysis of superstition and its influence on the philosophes, see e.g. Ernst Cassirer, The Philosophy of the Enlightenment (Princeton University Press, 1955), p. 160-182.

55. Quoted in Alexander, p. 23.

56. Philosophical Dictionary, "Atheism, Part I."

57. Ferdinando Galiani, quoted in Topazio, p. 18.

58. Topazio, p. 18.

59. D'Holbach's generosity is evident from his letters to Diderot. It is also worth noting that Jean-Jacques Rousseau, who was later alienated from D'Holbach's circle, still memorialised d'Holbach in Julie, ou la nouvelle Héloïse as the paradoxical character Womar -- a man who exhibits all the Christian virtues in spite of his atheism.

62. While most of d'Holbach's contributions to the Encyclopédie were on topics related to chemistry, he also wrote several disparaging articles on non-Christian religions. See the following: Newland, T. C. "D'Holbach, Religion, and the 'Encyclopédie'", Modern Language Review, Vol. 69, No. 3, (Jul., 1974), pp. 523-533; John Lough, Essays on the 'Encyclopédie' of Diderot and D'Alembert (London, 1968), pp. 1-29; Topazio, p. 16.

67. De l'esprit aroused the anger of the clerical authorities and copies were quickly burnt by the Paris hangman. Helvétius was consequently obliged to make at least three separate public retractions. See Isaiah Berlin, "Helvétius" in Freedom and Its Betrayal: Six Enemies of Liberty, ed. Henry Hardy, (Oxford: Oxford University Press, 2002), p. 11.